Got a little problem here

[rbahr]

I have a MAXJAX on order, so I started looking at my garage floor. Broke out the rotary hammer and decided to do a test hole to find out how thik the slab is. The bit made it about 3" in no time at all, and then that was it... the bit stopped going any deeper. First thought was rebar - so I got my magnetic pickup out, stuck it in the hole nothing ferrous in there. Next thought was ledge or a big rock. any thought or suggestions out there - besides the obvious 'I am so screwed'?

TIA

Ray

 

[d33pt]

try another hole?

 

[crashbumper]

try another hole?

Be careful, sometimes that will get you slapped.

HA!

 

[texmln]

Do you have a post-tension slab? If so, it's possible you hit a tendon, which is usually slathered in grease and covered up by a thick plastic cover. Between the two you might not see much magnetism from your pickup...

 

[nate379]

Is the bit ok? How old is the slab.

I have drilled in slabs that are 60-75 yrs old and they are darn near impossible to do compared to something just a few months/years old.

 

[rsanter]

I have drilled into concrete and hit a really hard rock that takes forever to go through. generally you can tell this if the color of the dust comming up changes. in the bast I have just kept going untill I went through it, but it was a pain.
go to another hole to see what happens, you can always come back to the first one

bob

 

[rbahr]

I had tried a second spot before I asked the group. Turns out that while trying to clean out the dust between drilling cycles, I was not getting all the dust out - so the bottom of the hole was finely powdered concrete dust. I tried using compressed air which worked better. Thanks...

Ray

 

[FunfDreisig]

I had tried a second spot before I asked the group. Turns out that while trying to clean out the dust between drilling cycles, I was not getting all the dust out - so the bottom of the hole was finely powdered concrete dust. I tried using compressed air which worked better. Thanks......

I found even compressed air leaves a lot of dust in the hole. I used a 1/2 dia. "kitchen bottle brush" and the little extensions for a shop vac (e.g. the accessories for cleaning keyboards etc.) to clean the holes for the 1/2" galv expansion bolts on my sill plates. And then followed it up with compressed air. It helps to really clean the sides of the hole, so that the expansion ring goes all the way in and wedges tightly on the way back up.

Funf Dreisig

 

[Torque1st]

A copper tube extension on a blow gun helps get the compressed air to the bottom of holes.

 

[nate379]

Shop vac has always worked fine for me. No sense blowing concrete dust all over the place anyhow.

 

[38Chevy454]

Sometimes if you run a punch down the hole and smack it hard to crack the hard rock it helps to get past a tough point.